The red dot sight is a reflective sight, the principle is similar to the reflective head-up display on an airplane or car. Because there is no magnification, it is suitable for aiming with both eyes and has a wide field of view.
However, it is easily affected by light, and the aiming point cannot be seen clearly under strong light. The figure below is the schematic diagram of the red dot. The light emitted by the red dot is parallel to your aiming line after being reflected by the lens, so the virtual image formed by the red dot on the lens is always on the aiming line. Due to the particularity of the human eye, it is seen by the human eye Now, this red dot is equivalent to the laser sight commonly used by special police in the movie. After the target is illuminated by the special police, the image in the eyes of the gunman is the same (but the inner red dot does not really illuminate the target), but you only have a transparent image. You can see it through the lens.
